staging: wlan-ng: Fix incorrect type in assignments

fc variable type was u16 and it has an assignment
from cpu_to_le16() so its type changed as __le16.
This bug found by sparse.

Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>